The present invention is directed to an SZ stranding method for skein-like stock which is conducted along an outside surface of a tube store, which has a longitudinal axis and is alternately rotated in a first direction and then a second direction on its axis, with a changing number of lays and then through a stranding nipple. In addition, the invention is directed to an improved stranding apparatus which performs the improved method.
Stranding of stranding stock, particularly in the form of electrical and/or optical conductors, by means of a tube store is known, for example, from U.S. Pat. No. 4,359,857, which claims priority from German Patent application No. 30 06 055. As disclosed in this U.S. patent, a tube store having a tubular guidance storage member is provided and one end carries a stranding disk or plate which is rigidly connectd thereto. The stranding stock is moved along the tubular store and through the stranding disk to pass through a stranding nipple. A known SZ stranding can be obtained by means of periodically changing a rotational direction of the rotation of the tube store on its axis.
A more precise examination of the operating mode of a known tube store apparatus or machine shows that a combination of sliding movement or translation and stranding upon roll-off of the stranding stock on the tube store occurs during the stranding operation. The combination of the translation and of the rotation or roll-off in a common pass leads to a certain limitation of the use possibilities of such a stranding method. Specifically, difficulties can occur when stranding elements having a high outer coefficient of friction or when a demand is made for a tube diameter in relation to the tube length and the respective number of lays mutually restrict one another. Moreover, depending on the relationship of the speed of rotation of the store and the stranding speed, the method always leads to a more or less complete backtwist, which is usually desirable given round elements but can be undesirable given profiled elements, for example, sector leads or cables which have a number of elements with the spacing or the gore filled. However, it is still desirable to have an SZ stranding for these types of elements.